Tower project

On the way for the construction of my tower.
Height: 15m – Base square section of 65 x 65 cm
Last year 2017, I finished the construction of my freestanding tower of 15m.
(The trolley is also on the way).
Finally, this week, I was finally able to finish the construction of the chair that will go into the concrete.
The formwork is 1.5m X 1.5m X 1.7m. - 90cm of earth and 60cm of rock made with the jackhammer!! And 20cm of formwork wood), about 6500 kg of concrete.
Fixation of the base plate in the concrete with 8 rods of 26mm diameter, length 1,4m.
Fixation of the tower on the base plate with 13 rods of 20mm diameter.
In case of very big wind!! (Sometime 80/90 km/h) 4 x 3m supports will be attached to the concrete diagonally at the 4 corners of the tower and 4 concrete blocks are provided for guying if necessary. It will should not move ...Hi
Today, 23/11, the concrete is finished. This project progressing slowly but surely.
(soon I'll add some pics of the trolley)

New Satellites antennas Setup

Sweat to make the antennas .. Finally, Ready to chasing satellites. 1st tests conclusive on 2m/70cm.. 23cm later !
2m cross Yagi and the helix gave me a lot of mods, settings and mechanics, finally it's over!
Seems to work fine. Contacted easily couple of satellites. 1st longs distances was on AO-7 mode B with:
- PT2AP grid square GH51JO at 6822 km. 06 April 2018
- PY2LN, grid square GG66PK at 6326 km. 20 May 2108

Will see to add somes preamp. and connect to test the 23cm yagi's soon.

Yagi antenna 35 el. 23CM

 Inspired by DL6WU, F9FT, DJ9YW

Always for the Fun and for some tests with the Satellites, I continued the construction of my antennas for the 1296 Mhz with the construction of some Yagis 35 elements. I did not want the elements to cross or be in contact with the boom, I chose the isolated version.
And 35 elements only on a boom of about 3m gives a gain of about 17.8 dBd. Sufficient for me between the ratio of the gain and the length of the boom.
I was inspired by the model and design of F9FT 23cm / 35el., But I built the dipole is symmetrical T rather than a Loop trombone.
To install the distant elements of the boom, I made some tests with supports like Y nylon columns  and  square support used to fix the ties wraps but it was inconclusive.
Having nothing else, I looked on the Web, supports already built for this kind of application at I0JXX.

Here are the references:
http://www.i0jxx.com/en/52-4mm

ISO15 4
Element diameter 4 mm Boom dimension 15 x 15 mm Distance from boom 40 mm
BOX4JXX
Nylon 6.6 box, it can be bored in order to put in dipoles and connector

Elements: 4mm diameter aluminum rod
Boom: 15mm square, length: 3m

This antenna is easy to build, the only care is the strict respect and the precision of the dimensions. I used EZNEC software - RF SIM 99 - Yagi Calculator by John Drew VK5DJ.

H Pattern

V Pattern

Ready for connection and First Tests.

Next descriptions: 4x12 el. 144Mhz, 4 x 25 el. 432Mhz, Mesh dish 3,2m F / d: 0.4

145Mhz Cross Yagi

2 x 10 el cross yagi 145 MHz. RHCP.
Feed system: adaptation of the dipole in T symmetrical match

The procedure is easy to take all elements and mount them at 90 degree angle on the same boom.
Traditionally circular polarization is generated by feeding two crossed dipoles 90 degrees out off phase. But you can also shift the dipoles 90 degrees in space and feeding then in-phase with the same effect. The advantage is that the two cables in the splitter have equal length and therefore gives identical transformation of antenna impedance
I prefer the mechanical method despite the electrical method (with different length of cable to obtain the 90 deg phase angle). So, I have shifted each V element exactly at ¼ Lambda forward on the boom. So the entire vertical antenna is shifted forward with reference to the horizontal antenna.
The forward shift (Offset) between the two dipoles is 517 mm to obtain 90 deg Phase angle.

Like this the two antennas are excited with a 90 degr. of phase shift. With this now a rotating field is radiated.
By shifting one section of the yagi forward by a quater wavelength the phasing cable to the two antennas becomes equal, impedances becomes equal and the antennas must share the power equally - regardless of the VSWR.
The two antennas must be feed with a splitter. An air line gives by the calculation an impedance of 35,35 ohms : 𝑍𝜆4⁄∗1√𝜀𝑟 =√𝑍𝑝∗𝑍0∗ 1√1 =√25∗50 ∗1= √1250=35,35𝛺
But mechanical splitter is too big at this frequency.
So the splitter can be made from two 75 ohm ¼ lambda equal length of coax cable.

On 144 MHz a quater wavelength coax is 1/4 x 300/144 x 0,66 = 340 mm (the real velocity factor of the coax used must be applied . In this case + 0.66, solid polyethylene dielectric).  I use three quater wavelength 75 ohm cable, which gives the same transformation. The cable length of 102 cm allows the point where the three coax ends are joined together far from the dipoles.
Software: For Yagi antenna, I use the VK5DJ John Drew software ‘’Yagi calculator’’ of http://www.vk5dj.com/yagi.html

 

Helix antenna 432/435 MHz 14 turns

After my first success with this kind of antenna in 1992 in VE2 land (antenna homemade helix 9 turns) see pic at Blanville, Quebec of my antenna set up, I decided to build another one with 14 turns.

VE2EK Antenna's set-up at Blanville (Quebec)

Wanting to further improve my Satellites antennas after the construction of the portable 2m / 70cm yagi cross, I set about building a 14-turn "Home-made" Helical Antenna for 432/435MHz.

This 50 ohm impedance antenna allows, when fed with 25/50W of SSB RF, to join the 'Molniya' orbiting satellites like AO-40 and AO-10 very easily!
The gain of this antenna is estimated at 16.5 dBd theoretical.
It's all about giving ideas on how to build a sustainable helicoidal antenna, rather than giving you a recipe to follow.

Calculations made with the HelixCalc Software.

Mesured Results with:
- Windfreak SynthNV: 34MHz – 4.4GHz RF Signal Generator/ RF Sweeping/ Power Detector
- Waterbeach Electronics WE-520A 520 Mhz Antenna Analyzer
                           435MHz, VSWR: 1.04/1, Return Loss: 33.17dB
                           433MHz, VSWR: 1.02/1, Return Loss: 40.1dB
                           432MHz, VSWR: 1.01/1, Return Loss: 45.2dB
Bandwith wide and OK for me!!

Note that for the construction of this antenna I chose round metric values;
The diameter of the wire used for the turns and according to ARRL "Antenne Book" should be between 0.006 and 0.05 Lambda.
The following materials were used to build the 14-turn helical antenna:
• Aluminum: 25mm square support, arms reflector supports,
• Teflon PTFE: Spacers
• Galvanized iron: Reflector grid, Bee hive origin !!
• Aluminum: Helical wire (6.35mm (1/4 "dia.) Plumbing pipe
• Stainless steel: All hardware, support.

Notes on the assembly:
• The central support is drilled every 1/2 turns to receive the Teflon PTFE spacers,
• The spacers are drilled for fixing the helical tube at one end. They are also drilled at the other end to be fixed inside the central support.
• Pieces of galvanized wire. are used to fix the turns to the central support in the spacers.
• I painted all steel surfaces with a polyurethane-silicone alkyd paint.
• The coaxial cable used on the antenna is: 10DFB up to the preamplifier. After the preamplifier, Andrew Heliax ½ cable.
• Connector used: Type N, female, panel mount.
• The reflector is designed so that it can be slid on the central support, in order to adjust the TOS. Two screws hold it in place once adjusted.
The final adjustment of the TOS is done by sliding the reflector forwards or backwards. The center pin of connector N, is fixed on the last turn which has a spacing between the back panel ranging from 13mm to 4 mm at the feed point.
**** this antenna can be fixed to the back of the panel with a counter weight or at its equilibrium point on its boom to an isolated support not to disturb the radiation.

See the diagram of the construction: